man I'm all confused now about oil, i know i shoul shut up about it and talk about sumthin else. Anyway, I heard that when using synthetic oils it should be used in newer cars rather than older cars with 100K + on the clock. And you should use synthtetic blend in older veichles with miles on them. Well, if this statemnt is true I dunno.

 

ive beed advised against using synthetic on engines with 80k miles or more because synthetic is a thinner oil and theres a very high chance that you will develop an oil leak if you do. regular oil has worked great for me, my 302 5.0 has 195,000 miles on the clock and its still ticking with no problems (well, some problems but its still running great!)

 

This is what I just copied from the MOBIL 1 web site. I too have just swapped my wifes 4 banger Plymouth Acclaim with 120k on the clock over because she only drives her car for short trips and only puts less then 200 miles a month. This car has got to last FOREVER too. At least until she gets a new job....... The F150 is going to get it soon too. Since I can get the 5 qt bottle at Walmart for $18.00, might as well!! Anyway, here is the quote.

Myth: Mobil 1 will leak out of the seals of older cars.

Answer: Mobil 1 does not cause leaks. In fact, new Mobil 1 with SuperSyn™ was tested in dozens of industry standard and OEM tests to prove its seal performance. It is fully compatible with the elastomeric materials from which all automotive seals and gaskets are made.

ExxonMobil engineers are wary of conventional oils that tout their use of additional seal-swelling agents. With extended use, these agents can over-soften engine seals, resulting in leaks. More to the point, an oil additive will not rejuvenate worn or damaged seals. The damaged seal may have been caused by a worn rotating metal component in the engine.

If an older engine is in good condition and does not have oil leaks, Mobil 1 with SuperSyn™ provides the same advantages as when used in a new engine. ExxonMobil recommends taking measures to repair the leaks, then using Mobil 1 with SuperSyn™. ExxonMobil also always recommends following the automobile manufacturer's manual for the proper oil to use.

 

well i dont know how much truth there is to that quote, but i do know a good friend of mine who has an 86 f-150 with a 300 inline six (10,000 miles since last rebuild) recently switched to synthetic oil and developed a small oil leak. he then went back to conventional oil and the leak went away (both oils were same weight). the oil he used was not mobil 1, however, so i really couldnt tell you for sure. i say try it and see. if it leaks, then go back to regular oil. good luck!

 

Oil can be a touchy subject around here. I’m going to tell you what I was told by a Mobil oil rep, but first a disclaimer. I don’t have an electron microscope. Therefore I cannot tell you if the molecules are the same or different in one oil vs. another. I didn’t verify any of this information by a real scientific study or even a study in my basement with a “my first science kit”. But here is what I think …

The story. I was a mechanic, been one for years. I worked at a Mobil station, and used Mobil oils. We would sell as many Mobil one oil changes as we could. Why? Because we believed it was the best oil money could buy (still do), and it made a nasty job more profitable. But, every once in a while (1 in 2000? I don’t know exactly) we would do an oil change on an otherwise non-oil leaking car. When the Mobil 1 was put in it would just come running out, or at least start leaking where there obviously wasn’t a leak before. In one 4100 GM engine is came out or the valve cover gasket as fast as we could put it in (as it was draining down to the pan). The only way to fix this was to fix the leak, or drain out the Mobil one and add dino oil. I saw this many (more than 3 less than 10) times. Ok, those are the facts as I know them.

Now, this is what the Mobil oil rep told me (what his qualifications are I have no idea). He said that the molecular structure of the Mobil 1 oil is more consistent than the Mobil dino oil. He said to think of the dino oil like a bottle of pebbles. Some are big, some are small, some in between. The Mobil one is like a bottle of BBs. They are all very close to the same size. So, if you have a hole BBs fit through, you got a leak. It is completely possible that you could have a leak where only a tiny bit of dino oil would leak out of that Mobil 1 would just run out of. Now of course, he did point out that an oil leak is an oil leak. If it runs out, the seal or gasket is to blame, not the oil.

With that said I used Mobil 1 in my F150 I had at the time until I sold it at 292,000 miles. I never once added a quart between changes. It was always in the safe range when I changed it (sometimes as long as 9000 miles between changes). So, no leaks and the engine lasted a long time. Now granted, I did fix leaky gaskets and seals now and then. But no surprises like a sudden nasty leak (obviously, since I never added any).

 

good info

 

adayjc, at what interval did you do your oil changes with Mobil1?

 

Great info, adaycj. The comparison of dino oil to synthetic using pebbles and BB's is right on. Synthetics flow more easily therfore, they will leak more easily. Synthetics don't cause leaks. They just get through the "holes" that dino oil can't get through.

If you're thinking about a synthetic blend, save your money. These blends are typically 5% (or less) synthetic. Go straight synthetic to get the best performance. If you still want a blend, mix it yourself.

 

My turn.

I bought my 94 in late Feb. It had 84k on the clock. The engine is amazingly clean and rust free, no leaks of any kind. I switched to Mobil 1 about 2500 miles ago. I just got back this weekend from towing a 6x12 trailer, about 1800 lbs empty and loaded about 2200 lbs, 7 hours each way. I drove I-77 through WV mountains to Ohio and had to maintain 65 in 3rd, not OD, most of the way. Needless to say I put a pretty good load on the engine. The 351 is strong and did it no problem. I didn't use any oil and still no signs of leak. I would have to agree with a couple people above, if your seals leak it's the seals fault not the oil. I believe the extra protection is worth the money. Considering I used to pay $26 per oil change at the Texaco place and now I pay roughly $20 ($17.88 for 5qt Mobil 1 @ wal-mart) I'm coming out ahead even if I change every 3000 miles. I'm probably going to try 6000-9000 mile changes. My friends BMW recommends 14-16k mile change intervals with full syn. He changes his oil once a year at the BMW lot and has had no problem. That's too long for me but I believe the oils are good for it. I plan to change the filter every 3000 miles.

 

Just to add the obvious.
What would you rather have flowing thru your engine and over your mains and then into your heads, fine uniform BB's or a bunch of different size rocks. If it doesn't get thru a leaky gasket then will it get where it is needed in the engine? I have 113,000+ (hard miles) on my 4.6 (slapper) and it is still running strong. I will only use Moble 1 in any engine regardless of the miles.

 

I'm not a engineer or have hard cold facts to prove this. I switched to Mobil 1 5W30 at over 120K and up untill now have seen no leaks (knock on wood). I have heard/read the same theory on the synthetics being a more unifrom size. I agree to the fact that if it does leak it's a fault of the seal not the oil.
I use to run 10w30 quaker 4x4 in mine before I new it called for 5w30, just beacuse that was what my dad use to run. After I learned better I went to the Mobil in 5w30 and noticed a smoother idle and the oil comes out a dark brown not black (which actually has no indication that oil is bad or good). I have tried running Mobil 10w30 and there was really not much difference. It might of made slightly more noise right on startup due to oil starvation or I could have imagined it. This test was done in the dead of winter with temps down to single digits. Just to make me feel better I went back to 5w30. My engine now has 136k on it and runs fine. It does have a few noises but nothing bad (at least not yet, knock on wood again). All you can do is give it a shot. If it leaks switch back, if not you've found your new oil.

 

Well, now that I have people talking about references to rocks in engines I want to add another story. Again it is my observations only, no studies, engineering or any other thing that modern society would call real facts.

First, to answer the question. I changed the oil at 9000 mile intervals for about 180,000 miles. I then changed to a 3000 mile interval because I moved and only drove 2 miles to work. The short trips meant I was actually harder on the engine, and only needed two oil changes a year, even with other usage. I'm not recommending any intervals to anyone. Just what I did.

Now, on to another story. When I moved to that place where I only drove 2 miles to work (actually I walked a lot), it was cold there. A few days during the winter it was -20 ish. Well, one day I needed to pick some stuff up at lunch, so I needed to drive to work. I went out side on a nice cold -17 degree (F) morning. There were many other people outside in the parking lot trying to get their cars started and warm them up. Most of them wouldn't crank fast enough to get them going. My old pickup spun up almost normally. I started it and drove away after a few minutes. Hours later, after a busy day at work (mostly working on cars that wouldn't start) most of the same ice covered cars were still in the lot. Most of them were much better overall than my F150. I think the oil helped considerably. Granted it’s a rather obscure benefit, but it helped in this one isolated case.

Despite the longevity of several engines I’ve run on Mobil 1 I still do not think it is really needed. I’ve seen many engines run over 250,000 miles with no problems on dino oil, it just happens to be the one I’ve had go that far ran Mobil 1.

 

When I switched to Mobil 1 in older engines, it started oil leaks that those motors never had. I've had great luck using Valvoline multi-grade through the years and am sticking with it. Use synthetic if you want, but I'll just keep changing the oil and filter every 2500 miles and using petrolium-based oil. It works for me.

 

On saturdays the local NAPA auto centers have a radio program where they answer car questions and this last Saturday they had on an oil rep. and he explained it like this:

Non synthetic is like holding TrailMix in your hand with all kinds of different sizes and shapes, when you crush it up and move it around it causes a lot of friction and heat.

Synthetic is like having ball bearings in your and and if you mash it up and move it around it has considerably less friction and heat--i.e. better gas mileage.

With all that said they advised to use the same oil that you have already been using in a high mileage engine because if you switch over it could cause leakes because seals may break. The were not trying to sell any make, brand or model of oil they were just telling what they knew about oil and I respect their opinions more then most. They also said that no matter the oil it still needs to be changed 3-5,000 miles, preferably 3,000

I may have been redondant in this post but I did not have time to read all the previous ones